Cold-water swelling starch ethers in original granule form



Patented 25,195)

IN ORIGINAL GRANULE FORM ooLn-wA'rEn SWELLING s'rancn'n'rnans Carl C. Kesler and Erling T. H jermstad, Cedar g i Rapidalowa, assignors to Penick & Ford, Ltd.', Incorporated, Cedar Rapids, Iowa, a corporation of Delaware No Drawing. Application August 13, 1 947, Serial No. 768,488

v '26 Claims. (Cl. 260209)' 'the partial etheriflcation of starch in its original anule form and with dextrinized starch. The present invention constitutes a continuation in part of our co-pending applications, Serial No.

688,976, filed August 7, 1946, and No. 740,718, filed April 10, 19-17, entitled Starch Ethers in Original Granule Form and Preparation of Starch Ethers in Original Granule Form, respectively.

It has been known for many years that alkylene oxides, particularly ethylene and propylene oxide, will react with carbohydrates to form hydroxyalkyl ether derivatives. The usual practice is to treat the carbohydrate material with an'excess of strong alkali, such as concentrated aqueous solutions of sodium or potassium hydroxide, before or during the reaction with alkyleneoxides. This type of process is best adapted to the treatment of cellulose. When starch is treated in this manner, its granules swell and rupture by the action 01' the strong alkali and depending on the amount of water present, either a paste or a doughy, plastic mass is formed. Upon reaction of these starch-alkali mixtures with alkylene oxides under diil'erent conditions a variety of products are obtained which are described in a number of diil'erent ways. Some investigators report doughy, sticky, translucent masses, some produced h'ard, glassy products, one produced an opaque mass having the consistency of honey or soft resin, while still others reported dark, yellow powders. In all of these products the granule structure of the starch has been either destroyed or irreversibly changed. These products require various special processing operations which are time-consuming and costly, for example, dialysis ofexcess alkali from solutions of the reaction product, neutralization of excess alkali with acetic acid ,and extraction of the sodium acetate by ethyl alcohol, extraction of the reaction product with alcohol, benzol, or other organic solvents, dissolving the reaction product in 40% alcohol and concentrating, precipitation of the reaction product with ether, evaporation of solutions of the product to dryness, and grinding of the product after drying. These products cannot be washed, dewatered or filtered, and dried by the ordinary methods and equipment used for producing commercial starches and starch modifications. Due to the difliculty, time required, and special equipment required for purifying these reaction products and also to the use of relatively costly organic solvents in some cases, the hydroxy-alkyl derivatives of the starches made by these methods have not been produced on a commercial scale, since the cost of manufacturing such products outweighs their commercial usefulness.

Some evidence has been published to-th'e eflect that dry commercial starches may be reacted directly with large amounts of alkylene oxides without first swelling or dispersing the starch with strong alkali. German Patents No. 368,413 and No. 363,192 describe the treatment of dry starch or cellulose with amounts of ethylene oxide from 10% to 3000% by weight on the starch with the production of materials which are described as being either starch-like or plastic, rubbery, or glassy masses. These specifications recommend the use of a large excess of alkylene oxide to promote the reaction and subsequent distillation oi the unreacted agent from the reaction product. The fact that a large amount of the alkylene oxide used in the process described is wasted is evident from the statement that the soluble, oily constituent formed may be extracted with alcohol or otherorganic solvents. The conditions of elevated temperature and pressure, and excess of alkylene oxide, favor the formation of soluble, oily materials from the alkylene oxide. Hydroxyalkyl ether derivatives of starch which have a tendency to swell in cold water can be made by the process described in these specifications but due to the inefliciency of the reaction the products are too costly to be of commercial importance.

While starch products having no tendency to swell in cold water can be easily made'by reacting very small amounts of alkylene oxides, for example 1% to 5% by weight of thylene or propylene oxide, based on the starch, with dry commercial starches as described in our co-pending application Serial No. 688,976 the combination of amounts of alkylene oxide suflicient to produce cold water swelling characteristics is not feasible by this process. Very long periods of time are necessary if larger amounts of etlwlene oxide are reacted directly with commercial starch at moderate temperatures and the reaction rate of propylene oxide and higher homologs is much slower. The reaction of suflicient propylene oxide with dry, granule commercial starch to produce cold-water swelling tendencies is extremely diiiicult. By raising the temperature and pressure or using a large excess of reagent the rate of reaction is increased "somewhat but this also results in the formation of greater quantities of side reaction products, usually oily or greasy in nature which are diflicult and costly to remove some 3 from the starch and which represent a substantial waste of etheriiyins a ent.

We have discovered that the efiicienoy and rate or reaction of larger amounts or alkylene oxides with 10% moisture mnule starch is greatly inv creased by incorporating inthe starch granules before reaction a small amount of a salt which will react with alblene oxides in the presence oi water to produce alkali. The emciency oi the reactionisincreasedtosuchanextentthatitis possible to-react with the starch large enough amounts oi alkylene oxides, such as ethylene and propylene oxide, to produce products having the original granule structure unchanged contain negligible side reaction products, and which will swell completely in cold water.

v A small amount soluble alkali may also be used. However, the proportion of soluble alkali which may be incorporated in starch granules without irreversibly altering the physical characteristics of the starch is very small. Soluble alkali, such as sodium or potassium hydroxide may be added to a starch-water suspension without swelling the starch granules provided the concentration of alkali is maintained below a certain critical value. This value depends on several factors, for example, the kind of starch, the degree or type of modification of the starch, the kind of used, the ratio of water to starch in the suspension, the temperature of the suspension, the presence or absence of substances which inhibit the swelling of starch, and the length of time the suspension is maintained in an alkaline condition. Dewatering and drying oi starch suspensions containing soluble alkali is feasible only ii very small proportions of alkali are present. Slightly swollen starch granules in suspension greatly retard the removal of water during the dewatering or filtering operation. After dewatering, commercial starches are ordinarily dried with heat. The presence of soluble alkali above a critical value will cause the starch to become darker in color or brown during the drying operation. This value also depends on several factors, for example, the kind of starch or degree of modification, the kind of alkali, the temperature, and the length oi time involved in drying. Due to the above mentioned difiiculties, it is not possible to incorporate sufilcient soluble alkali in starch granules to promote the desired reaction in many of the variations oi our present process. The incorporation of a salt in starch granules does not present these'difilculties, however. Salts such as sodium chloride or "sodium sulfate may be easily dissolved in starch suspensions and do not have a tendency to swell the granules or cause browning of the starch when it is dried at elevated temperatures. These salts act as latent alkaline catalysts in our present process. When an alkylene oxide is brought into contact with starch granules containing the salt and approximately by weight of moisture it reacts with the salt to liberate alkali. The amount of alkali liberated is sufilcient to promote an efilcient reaction between the starch and enough alkylene oxide to produce a product with unswollen granules and negligible side reaction protgucts and which will swell completely in cold wa r.

The amount of alkali present or liberated during the reaction must be less than that which would swell or change the granule structure of the starch. starches which contain approximately 10% by weight oi moisture and salt or alkali in amount insufilcient to cause swelling 01' the granules will react readily with alkylcne 4 oxides such as ethylene and propylene oxide to form products which retain the dry,"unswollen,.

granule form, are not colored, are not soluble in organic solvents, but which will swell completely in cold water to form, a smooth, viscid, colorless, and relatively clear paste.

The amount of alkylene oxide combined with the starch may be so limited to produce a product which will swell in water at any desired temperature between the normal gelatinization temperature of the starch and the freezing temperature 0! water. The amount of lowering. of the gelatinization temperature of unmodified corn starch by reacting with varying proportions oi ethylene oxide is illustrated in the iollowing table. Unmodified corn starchcontaining 1% by weight or sodium chloride incorporated in the granules was reacted with from 2 to 14% by weight of ethylene oxide.

suspended in cold water in a 5% dry basis concentration, neutralized, and their swelling temperatures determined by means of a Corn Industries viscometer. A description 0! this instrumentand method of determining gelatinization temperature ranges of starches is given in the Journal of Industrial and Engineering Chemistry, Analytical Edition, vol. 19: pp. 16-21; 1947. The cold water suspensions of the ethylene oxide reacted starches were placed in the viscometer and the temperature raised to the swelling temperature of ordinary corn starch over a period of approximately A hour. The temperature at which a substantial increase in viscosity occurred was recorded as the swelling temperature 0! the sample.

- TABLE Swelling temperatures of corn starch reacted with varying proportions of ethylene oxide Per cent by weight oi Swelling ethylene oxide Temperarescted w ture starch F. none 176 The partially etherified starches made by our improved process contain negligible side reaction products, even though amounts of ethylene or propylene oxide suillcient to produce cold water swelling characteristics have been reacted with the starch. The product remains in its original, dry granule form throughout the reaction and on completion of the reaction may be stored, packed in shipping containers, or used without any further processing operations. It needs no further purification or extraction. Our product is intended to have the natural form and physical properties of commercial starches and, in addition, lowered selatinization temperature range and absence of retrogradation and gelling tendencies.

Products can be readily made by our process which will gelatinize in cold water which is either acidic, neutral, or alkaline, and will swell at any dilution. This product swells completely in cold water, that is, there are substantially no unswollen granules or aggregates of granules which remain unswollen.

The reacted products were I .re meeazallw amexidermmormmmommerst ch s. mteinlaeeamnndsioq mywelzmz 11d salt casual-'-- :invtbe granules: be a st re misses; droxide and less than 5% by eightgpf m et-ba l lt ashln'gaiid discard ma as pr 7 ,ipres ntipmcess ylen oxid 't Lacid 'fddifid thin b'oiling;

ls iber du ediso'ann starches 'o'r' sex th'falkylen'e' oxides. Th'ei i h alkvl i o e r 'iniio'rmity" o dispersion'of the a q alka i" t e; h I

The temperature an I e'lnplo yedfin the process may vary widelyi "The reactionmay'be carried on at from belowa'ordinary or room temm e up to the qm eit n tem erat abo 'eprbelow that fifths-a osp re.

granule starch'fina'y' be-employed. "The term granule is'fintended to"describestarches which still hai'e' their original "granule structure intact; e'ven though may n ve-been sub'- sei iuen'tly modifled in many respects. starches havinga characteristic shape and size. During" the normal of"-'preparin g" commercial starches? these anules are not' altei'ed Phy callyl: :g'ranule structure is retained even during; such; treatments as fmodifying by means.

oiiiacidsionoxidiamg iagents ro'r' during the process ot-co'n'verting starch toidex'trins andgums. Gran- 1 the z. starches rgthereiore- 'include unmodified starches; tacid 'mOdiIiedv: thin: boiling starches, oxidized starches, British. gums, dextrins, and substantially all (it"fh" common commercial starches-, which" exist ;or ai-'e produced" iri "their original granule formh 'We alsdinclude the dif- 5 ierentqvarietiesnof starehp-sia'chas -co'rn' starch; potato starch, 1 wheat-starch, rice st'arch, waxy maize starch, :.,tapioca starch; whether modifle'd:

thcirrorigi-nalvzranulezIonnz'a'. welflnd nhstarehes respondJ-o :the: present process- 415.

lmlil outithfimfidefliribednfim :2.

The term alkylene oxides includes those com contain the ethylene oxide struc turemis illustrated by the skeleton formula Included therefore are ethylene oxide, which has thesstructural formula J ai faiprqpyieae oxide which has the structurtal formula.

--'I-'he term salt as used in this specification in cludes those salts which will react with an alkylene oxide in the presence of water to liberate free hydroxyl ions. Some examples of such salts are sodium chloride, potassium chloride, sodium sulfate, potassium sulfate, calcium chloride, ,etc. The term alkali includes those alkaliswhich liberate free hydroxyl ions in the pres enceof water.

. During the reaction of the dry starch with alkylene oxide, we prefer to admit the gaseous or liquid reagent gradually or in small, regular increments. In this way we may avoid high pressuresand alarge amount of unreacted alkylene oxide present in the reaction chamber at any given" time. It is known that alkylene oxides, especially ethylene oxide, may undergo dangerous exothermic polymerization under conditions of'high' pressure, elevated temperatures, and in the'presence of inorganic alkalis. By maintaining; onlya very slight excess of unreacted oxide in the reaction chamber at any given time we may thus avoid the danger of an explosion and also decrease the tendency of the unreacted alkylene oxide to undergo side reactions.

atahigheror lower moisture contents. The reaction is less rapid at lower moisture contents while at higher moisture contents there would be, a tendency for the starch granules to, swell as their. gelatinization range is lowered during the reaction.

After reaction with alkylene oxides the product may be neutralized with acidic materials o'r'leftinan alkaline condition. The degree or exte t of etheriilcation may be varied in accordancegwith the desired characteristics of the finisih'ed product. We prefer that the starch react with less than 20% by weight of ethylene oxide. The amount of alkylene oxide to be reacted is governed by the amount of lowering of the gelatinization range of the starch which is desired.

For example, we have found that 16% by weight ofethylene oxide reacted with an unmodified corn starch will produce a starch which will swell to a v'iscid, relatively clear paste within 5 minutes whenpla'ced in water at a temperature of 80 F.

" starches can be produced whichwill swell or gelatinize instantly in water at ordinary or room temperatures, or they may be made so that they require longer periods of time for complete swellingg 'A starch which will completely swell in 5 is more valuable for many purposes than one which swells instantly, since the tormer 7 would disperse in water readily before swelling. while the latter would tend to form algregates of ungelatinized granules covered with a tlhn of gelatinized starch,; which would be dlfllcult to disperse. The concentration of starch in a water suspension also has an effect on the rate of swelling.

Numerous attempts have been made in the past to produce .a' cold-water pastin starch which retains the bestcharacteristics of the original starch from which it is made. We have no knowledge of such a product other than that produced by the present method of treatment with an alkylene oxide. Pregelatinized starches, made by heating wet starch until gelatinized and dried I and subsequently grinding to a powder, have certain undesirable properties, such as partial retrogradation and the resultant tendency of part of the starch to remain undispersed when put in water opaqueness and coarseness of paste, and loss of'adhesive power. Chemical and thermal degradation ofstarchmay lower gelatinization temperatures, but atthe same time the viscosity of the paste greatly decreased. The

use of chemical agents such as strong alkali, in-

organic thiocyanates, formaldehyde, etc., to promote swelling or starches in cold water is either very costly or results in the introduction of undesirable ions in the paste, and necessitates pasting in a limited volumeof water to be efiective. The product we describe however, has none of the above mentioneddisadvantages.

The lowered gelatinization temperature range and the inhibiting, oi-the tendency of cereal starches to form gels when cooled after cooking suggests numerous industrial applications for this product. One of the 'serious disadvantages of cereal starches for many uses is the tendency of their pastes to set-back or retrograde. The glutinous starches, such as tapioca, which do not have this characteristic to such a marked degree have long been considered the best basis. for the preparation of adhesives. Also, the tacky or long character of the-pastes formed from the glutinous starches has been considered a valuable property in adhesives. For many purposes, such as in veneer glues, the adhesive must possess the ability to flow at relatively high concentrations. Ordinary cereal starches and many of their modifications tend to set-up or gel in high concentrations or lack the necessary flow properties. The treatment of cereal starches with alklyene oxides improves them considerably in this respect.

The products obtained by our present proeezs may be further modified by methods common in the starch industry. starches can be so reacted with alkylene oxidesv that when subsequently dextrinized by methods common in the starch industry give improved types of dextrins which when cooked have better flow characteristics and reduced tendency to set-back or stifien upon ageing. I

An ethylene oxide reacted corn starch functions eflicisntlyasa laundry finish, when the dry product is added directly to 100 F. water in the wheel of a commercial laundering machine, tumbling the clothes in the water for several minutes, extracting theexcess water, and then ironing. A firm, flexible, finish is produced on shirts, without streaks or shine. Cold water swelling starches produced by our process also are useful as home laundry starches, as they can be stirred with cold water to a stable, relatively clear, smooth paste which .will not gel on standing.

I 8 Boiling the starch and maintaining elevated temperatures are therefore avoided.

The cold water swelling alkylene oxide reacted starches may be used as thickeners in various commercial applications, for example, well drilling fluids and textile printing pastes. These starches are also excellent adhesives and may be used withoutcooking or heating in water at elevated temperatures.

The treatment of dextrins by our present process improves them considerably in many respects. Ordinary dextrins, particularly those made from cereal starches,such as corn starch, set-back or stifien on standing after being cooked in high solids concentrations in water. Dextrins which set-back or stiffen much on standing are not suitable for such applications as envelope and postage stamp adhesives, since the viscosity of the cooked dextrin must be kept within rather narrow limits to insure proper iunctioning oi the automatic machinery used in applying the adhesive to envelopes and stamps. They would also have a tendency to clog ieed lines especially dur ing periods when the machinery is shut down. Dextrins made from root starches,-for example, tapioca starch, do not possess this characteristic to such a marked degree and have been preferred for use in such adhesives. We' have found that the treatment of cereal starch dextrins with alkylene oxides by our present process reduces the tendency of the cooked dextrin' to set-back or stiffen on standing. T

If a sufficient proportion of ethylene oxide is reacted with corn dextrins, products are obtainable which are comparable to tapioca dextrins, with regard to their paste properties. Clearer films which have greater flexibility and less wrinkling on drying can be made with the dextrin products of our present process. Products can be made from corn dextrins by our present process which have the soluble and flow properties required by the Bureau of Printing and Engravingof the Treasury Department for use as an adhesive for gumming stamps.

EXAMPLE 1 Unmodified, powdered, corn starch containing approximately 10% moisture and 1% by weight of sodium chloride included in the granules is placed in a pressure tight reaction chamber equipped with means of agitation andtemperature control. After evacuating the reaction chamber to a 28" vacuum, ethylene oxide is ad-,

, EXAMPLE? Acid modified, thin boiling corn starch containing approximately 10% moisture and 0.5% by weight of. NaCl included in the granules is placed in a pressuretight reaction chamber equipped with means of agitation and temperature control. This starch has a maximum viscosity of 148 gram-centimeters when measured'in a Corn Industries Viscometer in an 8% dry basis concentration with a bath temperature-of 92 C.

The procedure for this test is described in the Journal of Industrial and Engineering Chemistry, Analytical Edition, vol. 19, pp. 16-21; 1947.

After evacuating the reaction chamber to a 28 inch vacuum, ethylene oxide is admitted in sufficient amount to maintain the pressure between 10 and 15 lbs. per sq. in. and the starch heated to 160 F. The starch is heated and agitated for 6 to 10 hours until 16% by weight of ethylene oxide has been absorbed or combined with the starch. The product obtained will have its granules intact and will completely swell in water at 80 F. to yield a relatively clear, smooth, and fluid paste, which will not thicken or retrograde on standing.

EXAMPLE3 Unmodified, powdered, tapioca starch containing approximately 10% moisture and 2% NaOH and 1% NaCl included in the granules is placed in a pressuretight vessel reaction chamber equipped with means of agitation and temperature control. After evacuating the reaction chamber to a 28 inch vacuum, ethylene oxide is admitted in suiiicient amount to maintain the pressure between 10 and 15 lbs. per sq. inch andthe starch heated to 160 1". The starch is heated and agitated until 14% by weight of ethylene oxide has been combined or absorbed by the starch. The product obtained will have its original granules intact and will swell in water at 80 F. to form a relatively clear, glutinous, and,

smooth paste.

EXAMPLE 4 Unmodified, powdered. corn starch containing approximately 10% moisture and 0.2% NaOH and 1% NaCl included in the granules is placed in a pressure-tight reaction chamber equipped with means of agitation and temperature control. After evacuating the reaction chamber to a 28 inch vacuum, propylene oxide is admitted in sufficient amount to maintain the pressure between l and 15 lbs. per sq. in. and the starch heated to 180 F. The starch is heated and agitated until 20% by weight of propylene oxide has been absorbed or combined with the starch. The product obtained will have its granules intact and will swell in water at 80 F. to form a smooth, viscid paste, which will not gel or retrograde on standing.

EXAMPLE Unmodified corn starch is suspended in a 1% by weight sodium chloride solution, dewatered in a suction filter to a cake containing approximately 50% by weight of moisture and dried to approximately 5% by weight of moisture. The starch is then dextrinized with acid and heat to a canary type dextrin, about 95% soluble in water. The dextrin is allowed to absorb moisture until its moisture content is approximately 5% by weight. The dextrin is then reacted in the manner described in Example 2 for 2 to 5 hours until 5% by weight of ethylene oxide is added. The reacted dextrin will form a fiuid paste when cooked in high solids concentrations in water and will have a greatly reduced tendency to set-back or stiiien on standing, as compared to the dextrin before treatment by our process.

EXAMPLES The product obtained in Example 1 is converted to a canary type dextrin by any of the usual methods. For example, 1000 lbs. of the products obtained in Example 1 is acidified with two lbs. of commercial muriatic acid and roasted in the range of 300' to 350 F. until the desired properties are obtained to meet the soluble and flow specifications of theBureau of Printing and Engraving of the U. 8. Treasury Department for use as an adhesive for gumming stamps.

While in the foregoing specification, we have set forth certain examples in detail for the purpose of illustrating specific modes of applying the invention, it will be understood that such details may be widely varied by those skilled in the art without departing from the spirit of our invention.

We claim;

1. In a process of the character set forth, the steps of intimately dispersing from .1% to .5% by weight of soluble alkali in a material selected from the group consisting of an unswollen granule starch and a cereal starch dextrin and containing from 5% to 15% by weight of moisture, and then gradually bringing into contact with said material from 1% to 20% by weight of a monofunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent' carbon-hydrogen groups at such a rate that no large excess of unreacted epoxide is present at any time and agitating the mixture in a closed zone until substantially no free epoxide remains.

2. The rocess of claim 1 in which the monoi'unctional epoxide is ethylene oxide.

3. The process of claim 1 in which the monofunctional epoxide is 1,2 epoxy-propane.

4. In a process of the character set forth, the steps of intimately dispersing from .1% to 5.0%

" by weight of a water soluble salt selected from the group consisting of the salt of an alkali metal and an alkaline earth metal in a material selected from a group consisting of unswollen, granule starch and a cereal starch dextrin and containing from 5% to 15% by weight of moisture, and then gradually bringing into contact with said material from 1% to 20% by weight of a monofunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups at such a rate that no large exces of unreacted epoxide is present at any time, and agitating the mixture in a closed zone until substantially no free epoxide remains.

5. The process of claim 4 in which there is added to the salt from .1% to .5% of soluble alkali by weight of material selected from a group consisting of unswollen, granule starch and a cereal starch dextrin.

6. In a process of the character set forth, the steps of intimately dispersing from .1% to .5% of soluble alkali in unswollen, granule starch containing from 5% to 15% by weight of moisture, and then gradually bringing into contact with said starch from 1% to 20% by weight of a monofunctional epoxide of a lower'aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups at such a rate that no large excess of unreacted epoxide is present at any time, and agitating the mixture in a closed zone until substantially no free epoxide remains.

7. In a procws oi the character set forth, the steps of intimately dispersing from .1% to 5.0% of a water-soluble salt selected from the group consisting of the salt of an alkali metal and an alkaline earth metal in unswollen granule starch containing from 5% to 15% by weight of moisture, and then gradually bringing into contact with said starch from 1% to 20% by weight of a monofunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups at such a. rate that no large excess of unreacted epoxide is pre-.

, by weight of a water soluble salt selected from the group consisting of the salt of an alkali metal and an alkaline earth metal in unswollen granule starch containing from to 15% by weight of moisture, and then gradually bringing into contact with said starch from 1% to 20% by weight of a monofunctional epoxide of a lower aliphatic. hydrocarbon, in which the oxygen is linked to adjacent carbon groups, at such a rate that no, large excess of unreacted epoxide is present at any time, and agitating the mixture in a closed zone until substantially no free epoxide remains.

9. In a process of the character set forth, the steps of adding to a water suspension of un swollen, granule fstarch an amount of a salt selected from the group'consistingof a salt of an alkali metal and an alkaline earth metal sufficient to result in a proportionof from .l% to 5.0% by weight of salt remaining in the starch on dewatering, then dewatering the starch to a moisture content offrom 5% to 15% by weight, gradually bringing into. contact with said starch from 1% to 20% by weight of a monofunctional epoxide of a lower *aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups at such a rate that no large excess of unreacted epoxide is present at any time, andagitating the mixture in a closed zone until substantially no free epoxide remains. a

10. The process of claim 9 in which the monofunctional epoxide isethylene oxide.

11. The process of claim 9 in which the monofunctional epoxide is 1,2 epoxy propane.

12. In a process of the character set forth, the steps of adding to a water suspension of unswollen, granule starch from .1% to .5% by weight of water-soluble alkali based on starch solids, then dewatering the starch to a moisture content of from 5% to-l5% by weight, gradually bringing into contact with said starch from 1% to 20% by weight of amonofunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adiacent carbon-hydrogen groups at such a rate that no substantial excess of unreacted epoxide is present at any time, and agitating the mixture in a closed zone unti substantially nofree epoxide remains. Y

13. In a process of the character set forth the steps of adding to a water suspension of unswollen granule starch from .l% to .5% by weight of water soluble alkali based on starch solids, and an amount of a water soluble salt selected from a group consisting of the salt of an alkali metal and an alkaline earth metal suificient to result in a proportion of from .1 to 5.0% by weight of said salt remaining in the starch on dewatering, then partially dewatere ing the starch, drying the starch to a moisture content of from 5% to 15% by weight, bringing into contact with said starch from 1% to 20% by weight of a monoiunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hygrogen groups whereby no substantial excess of unreacted epoxide is present at any time, and

agitating the mixture in a closed zone until substantially no free epoxide remains.

14. In a process of the character set forth the steps of adding to a water suspension of unswollen, granule starch an-amount of a salt selected from the group consisting of a salt of an alkali metal and an alkaline earth metal sufficient to'result in a proportion of from .1% to 5.0% byweight of salt remaining in the starch on dewatering, then dewatering the starch to a moisture content of from 5% to 15% by weight,

gradually bringing into contact with said starch from 1% to 20% by weight of a ,monofunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen islinked to adjacent carbonhydrogen groups at such a rate that no large excess of unreacted epoxide is present at any time, agitating the mixture in a closed zon'euntil substantially no free epoxide remains, and heating the product with acid to dextrinize the starch.

15.- In a process of the characterset forth, the

steps of intimately dispersing from .1% to .5%

by weight of soluble alkali in a cereal starch dextrin leaving a moisture content of from 5% to 15%, gradually bringing into contact with said dextrin from 1% to 20% by weight of a monofunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups at such a rate that no substantial excess of unreacted epoxide is present at any time, and agitating the mixture in a closed zone until substantially no free epoxide remains. j a

16. In a process- 'ofthe character set forth, the steps of intimately dispersing from .1% to .5% by weight of soluble alkali in an unswollen,

granule cereal starch leaving a moisture content of from,5% to 15%, gradually bringing into conof a monofunctional epoxide of a. lower aliphatic hydrocarbon in which the oxygen is linked to adjacentv carbon-hydrogen groups at such a rate that no substantial excess of unreacted epoxide is present at any time, agitating the mixture in a closed zone until substantially no free epoxide remains, and heating the product with acid to dextrinize the starch.

17. In a process of the character set forth, the steps of intimately dispersing from .1% to 5.0% by weight of a water-soluble salt selected from the group consisting of a salt of an alkali metal and an alkaline earth metal in a cereal starch dextrin leaving a moisture content of from 5% to 15%, gradually bringing into contact with said dextrin from 1% to 20% by weight of a mon ofunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups at such a rate that no substantial excess 01' unreacted epoxide is present at any time, and agitating the mixture in a closed zone until substantially no free epoxide remains.

18. Ina process of the character set forth, the steps of heating starch in which is intimately dispersed from .1% to 5.0% of a water-soluble salt selected from the group consisting of the salt of an alkali metal and an alkaline earth metal in the presence of an acid to form a dextrin, bringing the moisture content of said dextrin to 5% 13 agitating the mixture in a closed zone until substantially no free epoxlde remains.

19. A starch product comprising a reaction product of unswollen starch in its original granule form and 1% to 20% by weight of a monofunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups, said product prepared in accordance with the process set forth in claim 1.

20. A starch product comprising a reaction product 01' unswollen starch in its original granule form and 1% to 20% by weight of a monofunctional epcxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups, said product prepared in accordance with the process set forth in claim 4.

21. A starch product comprising a reaction product of unswollen starch in its original granule form and 1% to 20% by weight of a monoiunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups, said product prepared in accordance with the process set forth in claim 5.

22. A starch product comprising a reaction product of unswollen starch in its original granule form and 5% to 20% of a monotunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbonhydrogen groups, said product prepared in accordance with the process set forth in claim 1.

23. A starch product comprising a reaction product of unswollen starch in its original granso ule form and 5% to 20% of a monciuncticnfl 14 epoxide of a. lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbonhydrogen groups, said product prepared in accordance with the process set forth in claim 4.

24. A starch product comprising a reaction product of unswollen starch in its original granule form and 5% to 20% of a monofunctional epoxide 01 a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups, said product prepared in accordance with the process set forth in claim 5.

25. A material comprising a reaction product of a cereal starch dextrin and from 1% to 20% by weight of a monofunctional epoxide of a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups, said product prepared in accordance with the process set forth in claim 17.

26. A product comprising the acid degradation product of cereal starch reacted with from 1% to- 20% by weight or a inonofunctional epoxide or a lower aliphatic hydrocarbon in which the oxygen is linked to adjacent carbon-hydrogen groups. said product prepared in accordance with the process set forth in claim 14.

The lollowing references are of record in the file of this patent:

UNITED STATES PATENTS Name 7 Date Kreimeier et a1. May 10, 1938 Number 

1. IN A PROCESS OF THE CHARACTER SET FORTH, THE STEPS OF INTIMATELY DISPERSING FROM .1% TO .5% BY WEIGHT OF SOLUBLE ALKALI IN A MATERIAL SELECTED FROM THE GROUP CONSISTING OF AN UNSWOLLEN GRANULE STARCH AND A CEREAL STARCH DEXTRIN AND CONTAINING FROM 5% TO 15% BY WEIGHT OF MOISTURE, AND THEN GRADUALLY BRINGING INTO CONTACT WITH SAID MATERIAL FROM 1% TO 20% BY WEIGHT OF A MONOFUNCTIONAL EPOXIDE OF A LOWER ALIPHATIC HYDROCARBON IN WHICH THE OXYGEN IS LINKED TO ADJACENT CARBON-HYDROGEN GROUPS AT SUCH A RATE THAT NO LARGE EXCESS OF UNREACTED EPOXIDE IS PRESENT AT ANY TIME AND AGITATING THE MIXTURE IN A CLOSED ZONE UNTIL SUBSTANTIALLY NO FREE EPOXIDE REMAINS. 